Integrated geochemical-petrographic insights from component-selective δ238U of Cryogenian marine carbonates

November 1, 2016

Ash Hood, a NASA Astrobiology Postdoc in the department, and colleagues present the first uranium isotope results from different components of a ~650 million year old carbonate reef in South Australia. We found high variability in U isotopes between marine carbonates (e.g. microbial frameworks and marine cements) and
late-stage phases formed during the burial history. Large variability between poorly- and well-preserved phases within a single hand sample of rock may span almost the entire range of uranium isotope values seen in the modern Earth system. This work call for a fundamental change in carbonate trace metal work methodology  to make sure we thoroughly check samples for preservation before chemical analysis. In addition, the uranium isotope values of the best-preserved phases in these reefs reinforce the presence of anoxic and iron-rich oceans in
the lead-up to the rise of animal life. This paper has been promoted with a cover image for the November issue of Geology.

Ashleigh v.s. Hood, Noah J.Planavsky, Malcolm Wallace, Xiangli Wang, X., Bellefroid, E.J., Gueguen, B. and Cole, D., 2016, Geology, 34, p 935-938.